Performance of Lactating Cows Fed Alfalfa Hays Graded by Relative Feed Value System

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Abstract
The objective was to determine if the relative feed value system of grading alfalfa hays could predict relative performane of lactating cows. In 2 feeding trials, 32 Holstein cows in a 4 .times. 4 Latin square arrangement were fed rations containing 4 lots of hay. All hays were chopped and fed as part of a complete ration once daily. In the 1st trial, 2 lots of a number 2 and a number 3 quality hay by relative feed value were fed as 30% of the dry matter of the rations. Measurements of production were not different among groups. In the 2nd trial, cows were fed 4 rations containing hay of number 1, 2, 3 or 4 quality by relative feed value as 45% of the dry matter of the ration. Differences beween groups were of milk production (30.2, 29.1, 29.0 and 27.6 kg/day), milk fat (2.96, 3.21, 3.09 and 3.17%), persistency (100, 98, 98 and 96%) and feed intake expressed as percent of body weight dry matter (3.4, 3.4, 3.4 and 3.1%). Relative feed value should be used to compare alfalfa hay instead of quality grades.